Existing challenges in electrochemical energy conversion technology electrochemical energy-conversion devices, such as fuel cells and photoelectrochemical cells, face two main obstacles: significant overpotentials arising from surface kinetics and mass transport, especially at the Oxygen Reduction Reaction (ORR) in fuel cells and the Oxygen Evolution Reaction (OER) in water-splitting cells; and high catalyst mass loading that drives up costs and impedes the widespread adoption of these devices.
State-of-the-art commercial Pt/C cathodes for Proton Exchange Membrane (PEM) fuel cells exhibit specific Pt loading of 0.5 g/kW, arising from loading-per-functioning area of 0.5 g/cm2. While such fuel cells exhibit a high power density of 1W/cm2, they suffer from quick catalyst degradation, sluggish ORR with large overpotentials, and unsustainably large catalyst mass loading.
Graphene-like materials have been widely researched for electrochemical energy conversion devices, with claimed performances better than commercial Pt/Vulcan materials on some metrics.
In such a fast-moving field it is difficult to assess which routes are most promising, but it is seen that almost all existing schemes cannot maintain the most attractive features of graphene, such as high conductivity and carrier mobility. The main graphene-derived material studied so far has been Graphene Oxide (GO), a bulk material prepared through a sequence of harsh oxidation and reduction wet chemistry reactions. GO is economical but suffers from high resistivity due to numerous oxygen-containing defects. Moreover, the wet chemistry involved is often incompatible with further processing and large scale production necessary for eventual technological applications. At the same time, it is exactly these functional groups that provide GO with the ability to bond to catalyst nanoparticles and even facilitate oxygen anion transport, which pristine graphene cannot do on its inert basal planes.
Clearly, the ideal graphene material would overcome this trade-off. Such a material would have the necessary chemical functionalization but would retain pristine graphene's unique electronic and thermal transport properties.
What is needed is a material system that provides nanosized catalysts directly grown on chemically-activated graphene in a process that is cost-effective and entirely compatible with large-scale industrial production, in addition to preserving much of pristine graphene's outstanding properties, while activating the graphene toward catalyst-growth chemistry.